Figure 15a. Severe AVN of the talus with collapse of the talar dome. (a) Coronal CT scan through the talus shows a large hypoattenuating area surrounding an osteonecrotic segment of the medial talar dome, with a 1-mm articular step-off due to collapse of the medial articular surface (arrows). (b) Axial CT scan through the talar dome clearly depicts the large osteonecrotic segment (arrows), a finding that corresponds to the collapsed fragment seen in a.